Issue 61

A.A. ELShami et alii, Frattura ed Integrità Strutturale, 61 (2022) 352-371; DOI: 10.3221/IGF-ESIS.61.24

appear at their highest temperatures. TGA investigations revealed the decomposition of cement hydrates by diminishing increments on TGA curves and endothermic peaks on the derivative TGA. The degradation of cement hydrates can be separated into three stages [43]. The first phase occurs between 25 and 400, and in the second phase, the hydrates decompose between 400 and 600 °C, corresponding to the dehydroxylation of Portlandite (Ldx). Between 600 and 800 C, the third phase owing to CaCO3 decarbonation was reported as (Ldc). The first peak, which occurs between 25 and 400 oC, can potentially be split into two parts. Within the temperature range of 25–105 °C, the first phase corresponds to free water, and the second phase between 105–400 °C represents the dehydration reaction (Ldh). According to Loukili [44] and Monteagudo [45].Four mixes, M1, M4, M8, and M12, were chosen to be used in the test. Scanning Electron Microscope (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDS) The microstructure analysis was important because it simplified many of the concrete macrostructure's features and phenomena. Scanning electron microscopy (SEM) can be regarded as analyzing the CH and C-S-H layers in a concrete microstructure. The microstructure analysis was important because it simplified many of the concrete macrostructure's features and phenomena. Scanning electron microscopy (SEM) can be regarded as analyzing the CH and C-S-H layers in a concrete microstructure. The tested samples were collected from the innermost core of the crushed specimens after the compressive strength test at the age of 90 days. The test was carried out in the Faculty of Agriculture, Mansoura University, Egypt, using an electronic microscope of the type JEOL JSM-651OLV with a magnification capacity of 300,000 times. For the observation of specimens, five magnifications were chosen: 3000X, 1500X, and 1000X. Four mixes, M1, M4, M8, and M12, were chosen to be used in the test. An energy-dispersive x-ray spectroscopy (EDS) type (Oxford X-Max 20) was also used to determine the elemental composition of the observed specimens. Effect of magnetized water on the fresh properties of SCC lump flow and T50 cm tests: The slump flow and T50cm tests evaluate the self-consolidating concrete's deformability, flow-ability, and flow velocity in the absence of obstacles. [46] The results obtained are within EFNARC's acceptable limit. The results of the slump flow and T50 cm tests are shown in Figs. 2 and 3, respectively. According to EFNARC [47], the allowable slump spread for SCC is between 550 mm and 800 mm, and the time for the concrete to reach a diameter of 50 cm (T50) for all the mixtures was less than 5 s. All SCC mixtures showed flow time values in the range of 2–5. All results were within acceptable limits. Fig. 5 shows In comparison to the SCC control mix created with tap water, the use of magnetic water increased slump flow. This happens because the magnetized water molecules penetrate the layer more easily than tap water during hydration. As reported by [18, 48], cement particles repel each other due to the presence of magnetic water, which causes the production of hydration layers surrounding these particles, so the use of magnetized water had a positive impact on the mix's workability. As shown in Fig. 5, when water passes through the magnetic field 150 times rather than 100, a higher slump value is achieved in all SCC mixes. The effect of using magnetized water becomes more prominent as it passes through the magnetic field more often [49]. However, with the presence of silica fume, the workability decreases in comparison with control [50]. With increasing silica fume content, the workability decreases [51]. Fig. 6 depicts the T50 results, which show that magnetized waters cause T50 to decrease with increasing magnetization cycles [52]. S R ESULTS AND DISCUSSION

Figure 5: Slump flow of SCC mixes with or without Silica fume modified with magnetized water or regular tap water.

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